Paved roadbed

ABSTRACT

A paved roadbed composed of a lower roadbed layer, an intermediate layer made of sulfur, an upper roadbed layer and a surface top layer, the overall thickness of the upper roadbed layer and surface top layer being greater than about 8 inches and the sulfur layer being positioned atop the existing water table and being about 4-12 inches thick.

United States Patent n 1 j 111 3,858,999

Kadono et al. 4 Jan. 7, 1975 l l PAVE!) ROADBED 773,276 10/1904 Clausen 106/138 [751 Yahiko Kadono Tokyo; 322232 Zllfil 323E531: 106,98 Nakazaw, .0mIya;'Eiihi Miura, l,507,282 9/1924 Hammatt 404/28 Yokohama; Thunekathu Kitamura, 1,955,421 4/1934 I Muroran, all of Japan 2,225,458 12/1940 3] SSign-ee Nippon Oil C mpa y td. o yo, 2,353,027 7/1944 Goodwin 404/28 Japan r [22] Filed; 5 t 19, 1973 Primary Examiner-Nile C. Byers, Jr.

211 App]. No.: 417,081

[30] ForeignApplication Pribrity Data [57] 2 ABSTRACT Nov, 24, i972 Japan 47-l l72l7 I A paved b' mp s f a lower roadbd layer an intermediate layer made of sulfur, an upper road- [52] [1.8. CI. 404/27 bed layer and a Surface mp laycl. the Overall thickness [51] ll ll. Cl. E010 f the pp roadbed layer and surface layer being [58] Field of Search 404/17 greater than-about 8 inches and the sulfur layer being 7 f 196/287 27 138 positioned atop the existing water table and being b t.4-l2' h th' k. e r [56] References Cited 3 Ou mc es UNITED STATES PATENTS V 9 Claims, l Drawing Figure 517,823 4/1894 Mead et al 404/27 PAVED ROADBED BACKGROUND OF THE INVENTION This invention relates to paved surfaces such as roads or parking lots.

Heretofore, pavedsurfaces, specifically roadbed surfaces are in general composed of an upper roadbed layer and a lower roadbed layer. In certain cases only a single layer is used, but even in these cases a single layer alone being used, a top surface layer is always rolled for safety purpose. Accordingly, it may safely be. said that the upper portion ofthe bed thus rolled is substantially a kind of roadbed. Throughout the specification, the invention is described in terms of a roadbed of the type both an upper and a lower roadbed layer.

Typical roadbed materials, which have been conventionally used, are sandy soil, gravel and crushed stone. It has been a common practice to have these roadbed materials paved and rolled, so as to provide a desired roadbed. However, conventional roadbed materials present various problems, especially under the severe weather condition.

For instance, in the cold season, the roadbed becomes frozen and develops the so-called frost heave phenomenon. Particularly in the extremely cold regions, a paved surface frequently suffers frost heaves of up to 0.5m (1% feet) due to the soil freezing.

If such a phenomenon isnot experienced, the conventional paved roadbed has been nevertheless accompanied with other drawbacks such as susceptibility to surface cracking, poor drainage and overall shorter life. Furthermore, the conventional paved roadbed is disadvantageous from the viewpoint of economy, because a lot of time and labor are necessary for the maintenance and repair thereof.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a paved roadbed which is free from the above-described drawbacks, and which'is resistant to severe weather conditions such as frost heaves and resistant to cracking.

Another object of the present invention is to provide a paved roadbed which is superior in drainage and insulation so as to maintain a'road surface in good condi tion.

According to a preferred embodiment of the present invention, a paved roadbed is composed of a lower roadbed layer, a layer made substantially of sulfur, an upper roadbed layer and a surface layer, all of which are superposed in the order described directly or through the interposition of another layer. It is preferable that the overall thickness of the afore-said upper roadbed layer and surface layer combined be more than about 20cm (8 inches). It is preferable that the afore-said sulfur layer be positioned upwardly of the ground water-level and have a thickness of 10 to 30cm (4 to 12 inches) or thereabout.

It has been found that sulfur possesses properties I which are extremely appropriate in utilization for roadbed construction. Specifically:

1. An excellent drainage ability: Conversely,

Rain water, which has ingressed through the upper roadbed layer to the sulfur layer, is rapidly discharged downwards to the lower roadbed layer. Conversely the.

underground water table rising upwardly through the lower roadbed layer due to its capillary action, is inter- I rupted by the sulfur layer, since no capillary phenomenon occurs in the sulfur layer due to its excellent drainage ability. Thus, the first heaving phenomenon is perfectly prevented.

2. A low heat conductivity: The heat conductivity of sulfur is about 1/2 of that concrete and about one fourth that of stone. The sulfur layer, in the cold sea son, protects the lower roadbed layer from being frozen from above, due to its insulating property.

The present invention contemplates therefore an improvement in paved road surface, by utilizing two known but heretofore unex ploited properties of sulfur; It has been proven through experiments that the paved roadbed according to the present invention undergoes no adverse influence under the severe weather condition existing in the extremely cold regions, and no frost heaving phenomenon, with the result of a notably longer service life.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection withthe accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING The accompanying drawing is a longitudinal sectional view illustrating an example of a paved roadbed according to the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENT Referring to the drawing, the roadbed comprises a lower roadbed layer 1 which consists of a roadbed base 2 formed by leveling the natural ground and an overlying layer 3 of any conventional roadbed material such as sand. As an alternative, the layer 3 may be formed by rolling directly the roadbed base 2 without using a roadbed material.

Atop the lower roadbed layer there is a layer 4 formed substantially of sulfur. Sulfur used therein is solid sulfur such as grainor flake-shape. The sulfur layer 4 is not always percent sulfur, but may be made substantially of sulfur.

The sulfur layer'4 has a thickness of about 10 to 30cm (4 to 12 inches). The thickness of the sulfur layer depends upon the application condition, the nature of the sulfur used, and the type of pavement to be layed. A sulfur layer of a thickness less than 10 cm (about 4 inches) results in the failure of providing the intended water level interruption and insulating effect. Conversely, with a thickness of more than 30cm (12 inches) or thereabout, the pressure resistance CBR to the load becomes worse to lower the supporting force. The pressure resistance CBR is specified in JIS-A12l0 entitled A stamping type of soil compacting test. Generally, a paved roadbed requires a CBR value of 20 orthereabout.

The sulfur layer 4 is positioned atop the water table or underground water level 5. Should the position of the sulfur layer be lower than the water table 5,'this results in' the failure of producing the intended waterlevel interruption and insulating effect.

Atop the sulfur layer 4 there is provided an upper roadbed layer 6. It is preferable that the upper roadbed layer 6 be formed of conventional roadbed material, or a material of small particles, whose particle size is determined in consideration of the particle size of the lower roadbed layer 1. This, however, is a matter not critical to the present invention.

Over the layers 7, 8 and 9 there is a surface layer 10, v the upper surface ofwhich corresponds to the so-called road surface 1 1. The various types of pavement such as asphalt pavement, macadam pavement, concrete pavement, cinder block pavement etc. depend, therefore, upon the type of road surface ll employed. The overall thickness of the surface layer 10 and upper roadbed layer 6 should be more than cm. (about 8 inches) With a total thickness of both layers less than 20cm (about 8 inches), there arises a problem in the pressure resistance CBR, as described. Reference numeral 12, finally, indicates the atmosphere above the roadbed What is claimed is: 1. A paved roa'dbed comprising: a lower roadbed layer; a layer formed substantially of sulfur and positioned over said lower roadbed layer; an upper roadbed layer positioned over said sulfur layer; and a surface layer positioned over said upper roadbed layer.

2. A paved roadbed as claimed in claim 1, wherein the'overall thickness of said upper roadbed layer and said surface layer is more than about 8 inches.

3. A paved roadbed as claimed in claim 1, wherein said sulfur layer is positioned upwardly of the water table.

4. A paved roadbed as claimed in claim 3, wherein said sulfur layer has a thickness ranging from about 4 to about 12 inches.

5. A paved roadbed as claimed in claim 1, wherein said lower roadbed layer includes a base of levelled natural ground, and a layer of roadbed material positioned over said base.

6. A paved roadbed as claimed in claim 5, wherein said roadbed material is sand.

7. A paved roadbed as claimed in claim 1, wherein said sulfur layer is solid sulfur selected from granular sulfur and flake sulfur.

8. A paved roadbed as claimed in claim 1, wherein said upper roadbed layer is composed of a lower layer of unscreened gravel an intermediate layer of crushed stone and an upper layer of foundation crushed stone.

9. A paved roadbed as claimed in claim 1, wherein said surface layer comprisesa top surface selected from asphalt, concrete, cinder block and macadam. 

1. A PAVED ROADBED COMRPISING: A LOWER ROADBED LAYER, A LAYER FORMED SUBSTANTIALLY OF SULFUR AND POSITIONED OVER SAID LOWER ROADBED LAYER: AN UPPER ROADBED LAYER POSITIONED OVER SAID SULFUR LAYER:
 2. A paved roadbed as claimed in claim 1, wherein the overall thickness of said upper roadbed layer and said surface layer is more than about 8 inches.
 3. A paved roadbed as claimed in claim 1, wherein said sulfur layer is positioned upwardly of the water table.
 4. A paved roadbed as claimed in claim 3, wherein said sulfur layer has a thickness ranging from about 4 to about 12 inches.
 5. A paved roadbed as claimed in claim 1, wherein said lower roadbed layer includes a base of levelled natural ground, and a layer of roadbed material positioned over said base.
 6. A paved roadbed as claimed in claim 5, wherein said roadbed material is sand.
 7. A paved roadbed as claimed in claim 1, wherein said sulfur layer is solid sulfur selected from granular sulfur and flake sulfur.
 8. A paved roadbed as claimed in claim 1, wherein said upper roadbed layer is composed of a lower layer of unscreened gravel an intermediate layer of crushed stone , and an upper layer of foundation crushed stone.
 9. A paved roadbed as claimed in claim 1, wherein said surface layer comprises a top surface selected from asphalt, concrete, cinder block and macadam. 